On a cold winter day, a penny (mass 2.50kg ) and a nickel (mass 5.00kg ) are lying on the smooth (frictionless) surface of a frozen lake. With your finger, you flick the penny toward the nickel with a speed of 2.10m/s . The coins colide elastically, calculate both their final speeds.

The coins collide elastically; calculate both their final speeds.

What are the directions of their final velocities?
opposite or the same?

Question

On a cold winter day, a penny (mass 2.50kg ) and a nickel (mass 5.00kg ) are lying on the smooth (frictionless) surface of a frozen lake. With your finger, you flick the penny toward the nickel with a speed of 2.10m/s . The coins colide elastically, calculate both their final speeds. 

The coins collide elastically; calculate both their final speeds.

What are the directions of their final velocities?
opposite or the same?

mos1635 · Answer

|dw:1334347688353:dw|
no external forces => aplay persevation of momentum
elastic colition=> aplay conservation of kinetic energy
solve equation system
that gives you V1' and V2'
if value of V1' found <0 => oposite direction than shown on figure...